The summer of 2013 proved to be an eventful one for Mumford & Sons. In the past three months, the British quartet’s adventures have included a member's emergency brain surgery, being booted out of an Atlanta strip club, and performing to arena-size crowds far larger than what banjo-based bands traditionally draw.

Mumford & Sons was the right band at the right time to bring acoustic anthems to the masses. Since the release of “Sigh No More” in the United States in early 2010, Mumford’s ascent has been steep. The band’s second full-length release, “Babel,” was among the best-selling albums of 2012, and won the Grammy for album of the year.

Monday evening’s rescheduled concert amounted to a mini-festival alongside the Mississippi River, equal parts rural and urban. Attendees tramped through overgrown fields that served as parking lots, then walked the length of the sprawling Mardi Gras World studio complex to arrive at the vast concrete plaza at its western end, where food trucks and beer vendors hawked their wares. The Crescent City Connection and the towering smokestacks of a long-abandoned power plant provided the dramatic backdrop for a temporary stage.

The same site hosted the BUKU electronic music festival in March. Residents at least as far away as Bywater complained about sound waves traveling downriver. Perhaps mindful of keeping the peace, the first of Monday’s two opening bands commenced at 6 p.m.; the whole show concluded by 10. And Mumford & Sons generated far less bass than BUKU.

Because of the instrumentation – mostly acoustic guitars, banjos, upright bass, keyboards – and literary slant of the lyrics, Mumford & Sons is often described as “folk rock.” A more accurate designation would be “arena folk.” Their music’s broad strokes are meant to rally large groups of people to full-throated sing-a-longs. Had Mel Gibson filmed his medieval epic “Braveheart” 15 years later, Mumford & Sons could well have provided the battle sequence soundtrack.

Case in point: “Holland Road,” with its majestic sweep of horns, and lyrics describing how “you cut me down,” but “when I’m on my knees, I’ll still believe.” The battle Mumford recounts was personal, but could well have been waged on the plains of Scotland.

Going forward, Mumford & Sons’ challenge will be to avoid repeating themselves. Arrangements tend to follow a similar blueprint: Plaintive, stripped-down opening of voice and acoustic guitar. The banjo kicks in, followed by a rapid acceleration and build-up courtesy of increasingly frantic strumming, four-part harmonies and guitarist/singer Marcus Mumford’s right leg working a bass drum.

And so it went for 18 songs for nearly two, sweaty hours at Mardi Gras World. The primary four musicians arrayed across the front of the stage – Dwane, Mumford, keyboardist Ben Lovett and banjo player Winston Marshall -- eased in with the opening “Lovers’ Eyes,” beefed up by an auxiliary violinist and three-piece horn section. They dispensed with “Little Lion Man,” the band’s breakthrough, as the second song, stretching and toying with its harmonies. For “Whispers in the Dark,” Dwane switched to electric bass as Lovett took up an electric guitar.

The harmonies of the low-key “Timshel” were especially sharp. Energy surged through “I Will Wait” and the even bigger “Lover of the Light.” On the latter, Mumford thumped a full drum kit as Marshall channeled a guitar hero on banjo.

With the stage bathed in red lights, they showcased the ominous “Thistle & Weeds,” with Mumford on electric guitar, Marshall on electric bass, and Dwane on drums. They downshifted further for the delicate “Ghosts That We Knew.”

Just as quickly, they returned to arena folk mode with “Below My Feet.” The build-up led to a huge pay-off; Marshall wrestled with an electric guitar, conjuring un-folk-like feedback.

Humidity, even after sundown, was a factor, perhaps accounting in part for the frequent re-tuning and instrument-swapping between songs. “I’ve never been so sweaty in my ----- life,” Mumford said, noting the weight-loss opportunities afforded by touring in such conditions.

The encore opened with “House of the Rising Sun.” The Animals’ 1964 hit is the best-known version of a folk song whose origins date back centuries. With Marshall apparently making his public debut on drums, M&S rendered it as a spooky, brooding anthem. Mumford restored the original, female perspective of the lyric (“it’s been the ruin of many a poor girl”).

The finale featured a local ensemble that also is enamored of acoustic instruments: The Preservation Hall Jazz Band, the guest musicians of choice for visiting rock stars wanting to add local flavor to their New Orleans performances. At first, Mumford & Sons essentially turned the stage over to the Preservation Hall crew, which was augmented by guest trombonist Glen David Andrews and drummer Jason Marsalis. Pres Hall trumpeter Mark Braud sang “When the Saints Go Marching In” and led the audience in a “Who Dat” chant as the Mumford boys enjoyed themselves.

Braud and his bandmates moved to the side of the stage alongside the Mumford horn section for a final, all-out charge through “The Cave.” It followed the band’s blueprint, to great effect.

It was all big fun, but the most telling moment occurred at the conclusion of the regular set. For “Dust Bowl Dance,” Mumford returned to the drums, thrashing, bashing and knocking over the microphone stand. He channeled the rage and resignation of a teenage farm boy bent on avenging his family’s ruin at the hands of “liars and thieves” who “took it all from the weak hands of the poor.”

Despite the trashed drums, even Woody Guthrie may well have approved. This was arena folk at its rowdiest.